1. Field of Invention
This invention relates to compositions for topical application to the human skin.
2. Prior Art
The human skin serves a variety of functions which include the protection of the body from the external environment. The skin accomplishes this task in various ways one of which is the production of skin lipids the main source of which is the sebum exuded by the sebaceous glands of the skin. The sebaceous gland exudate, upon spreading over the skin, tends to thicken and form a protective layer that is lubricious and emollient, thus contributing to the suppleness of the skin as well as conserving skin moisture and providing an inhospitable environment for the survival of pathogenic microorganisms on the skin. Sebum, the skin's endogenous lubricant, consists of about one-third cis-6-hexadecenoic acid and its triglyceride and wax esters. Man is the only animal whose skin is known to manufacture this lipid substance, and until recently it was not known to exist in nature anywhere except as a constituent of human sebum.
In order to supplement or supplant the lubricious and protective properties of human sebum for cosmetic or therapeutic purposes it is common to apply oily or creamy emollient compositions to the skin. These emollient compositions contain lipid substances and may be in the form of creamy aqueous emulsions or in the form of creamy blends or emulsions of nonaqueous (eg., organic) substances. In addition to the lipid constituent or constituents (and, in the case of aqueous creams and lotions, water and oil emusifier) these compositions may contain an almost infinite variety of other ingredients such as perfumes, colors, preservatives, stabilizers, thickeners, moisturizing agents and medicinal substances, depending upon the intended use of the composition (eg., cosmetic or therapeutic). In all cases, these compositions contain as the principal lipid constituent thereof one or more oils or fats derived from animal, vegetable or mineral sources. However, to date, all of these oils and fats are largely composed of substances not normally found on the human skin surface. They may perform their emollient and protective functions well enough, but they are nonetheless foreign substances as far as the skin's normal biochemistry is concerned and may occasionally be the cause of allergic reactions and similar disturbances of the skin. Moreover, many lipids of animal and vegetable origin provide a fertile growth medium for mold and pathogens necessitating the use of preservatives in the composition which may also irritate the skin.
It has recently been found that the oil of the seed of certain plants, and in particular plants belonging to the Thunbergia genus, is composed predominantly of the triglyceride and wax esters of cis-6-hexadecenoic acid. After an intensive investigation I have discovered that this oil, and highly purified cis-6-hexadecenate fractions thereof, can be combined with water and other fluid vehicles to form aqueous and non-aqueous creams and ointments that have outstanding emollient and protective properties when applied to the human skin. Furthermore, since the lipid constituent of my new emollient composition comprises a fat natural to the human skin, the small but significant number of allergic reactions encountered with the foreign oils and fats currently employed as emollients is largely eliminated.